Wallet.loadFromFile takes WalletExtensions to deserialize

[kmels]

When saving a wallet with an extension, i would like to get the wallet including the extension back without using parseToProto(input).

[coveralls]

Changes Unknown when pulling 05f199e on kmels:load-wallet-file-using-extensions into * on bitcoinj:master*.

[mikehearn]

You can already do this by just instantiating your own WalletProtobufSerializer, adding the extensions to the wallet and then deserializing into it. However we have no documentation beyond the javadocs for wallet extensions so I am not entirely surprised you don't know this. Also the API is rather confusing and could need a redesign. But is this the right design?

[kmels]

Yes I know, however I was rather surprised by how the following snippet seems idiomatic yet it throws an exception when the default deserializer doesn't consider extensions. I believe the API should support the inverse operation automatically, but the API used is Wallet and not WalletProtobufSerializer.

Wallet w = new Wallet(..);
File f = new File(..);
WalletExtension ext = ...
extendedWallet.addExtension(ext); //ext can be mandatory
extendedWallet.saveToFile(f);
Wallet wallet = Wallet.loadFromFile(f); //exception, serializer can't deserialize.

If we want to discuss right API then in my opinion a Wallet should contain a serializer (WalletProtobufSerializer) that contains supported extensions itself, and an instance of a wallet can be made from a file. The serializer should be a singleton but also be able to be overriden, not sure if this is possible.. perhaps i should implement another reader as you suggest. 👍

In my case I use scala and I don't extend the Wallet class, instead I have a metadata class that persists these extensions and helps me retrieve a Wallet that is consistent. By consistent I mean that wallet implies metadata (owner's checksum) and metadata verifies wallet. I know i am replicating but i am trying to "scale" different wallet files.

[mikehearn]

this method shouldn't be necessary, surely? loadFromFile(file) still works with the above prototype change. It's source (probably not binary) compatible.

[kmels]

Thanks for reviewing. I made some changes

[mikehearn]

Merged and added you to the AUTHORS file, thanks!